On the Correlation between Formability and Nonmetallic Inclusions in Low Carbon Rimmed Steel Sheet.

Study of nonmetallic inclusions in low carbon rimmed steel-I

Abstract

A study was carried out to know the correlation between formability and non-metallic inclusion in low-carbon rimmed steel sheets.
The specimens were made from 6·5 to 15t ingot, basic open hearth furnace steel.
Formability of the sheet was measured by Erichsen and torsion tests.
The results obtained are as follows:
(1) Stretchability of 0·8mm cold rolled annealed steel is reduced by large sulphide (MnS) aad scum (over about 100μ long).
(2) Plenty of the above mentioned large sulphide (MnS) is precipitated as the content of sulphur reaches 0·035 to 0·040% in sheet. In that case, coarse lamination of hot milled steel is liable to occur.
(3) The lengths of inclusions measured along the rolling direction of a ore are mostly below about 25μ, in hot milled sheets. Moreover, authors confirm by diffraction of electronbeam that there are MnS, MnS· (Mn, Fe) O, α-Al₂O₃ (Corundum), α-SiO₂ (Cristobalite), Al₂O₃·SiO₂ (Kyanite), FeO·Al₂O₃-MnO·Al₂O₃ (Spinel), 3FeO·Al₂O₃·3SiO₂-3MnO·Al₂O₃·3SiO₂ (Garnet), 2FeO·SiO₂-2MnO·SiO₂ (Olivine) in hot milled sheet.